1. Field of the Invention
The subject matter herein concerns the addition of a connection identifier to an existing power saving class and more particularly, the addition of such an identifier without interrupting a sleep mode availability scheme.
2. Description of the Related Art
In current communication systems that operate in accordance with IEEE standard 802.16e, a mobile unit may be associated with one or more power saving classes (PSC), although each mobile unit is typically associated with a single PSC. A PSC defines sleep and listening windows for the mobile unit assigned to the PSC. The time period that exists when no listening window exists for all the PSCs to which a particular mobile unit is associated is referred to as an unavailability window, assuming that all the connections of the mobile unit are associated with a PSC. Thus, the unavailability window represents a time when the mobile unit is in a sleep period for all of its associated PSCs. During the unavailability window, a base station may not transmit to the mobile unit, which permits the mobile unit to power down certain components or perform other activities that do not require communication with the base station. The unavailability window is important in mobile communications because it permits the mobile unit to conserve battery power and allows for co-existence schemes with other radio technologies for avoiding interference.
As is known in the art, when a mobile unit is associated with a PSC, all the connection identifiers (CID) of that mobile unit are assigned to the PSC. Eventually, the mobile unit may wish to have a new service flow activated. Because the existing PSC will not contain the CID of the new service flow, this PSC will need to be deactivated, re-defined to include the new CID and then reactivated. This process is illustrated in the flow diagram of FIG. 1. In this drawing, signals originating from the left are sent from a mobile, while signals emanating from the right are transmitted from the serving base station. In addition, the shaded areas represent unavailability windows (see explanation above) and the lighter regions signify availability windows, or time periods where it may be possible for the mobile unit and the base station to exchange signals. In this scenario, it can be assumed that the mobile unit is associated with a single PSC and wishes to initiate a new service flow.
Initially, the mobile unit transmits a dynamic service addition request (DSA-REQ) to the base station during an availability window or interval. The base station responds by transmitting—during the next availability window—a dynamic service addition response (DSA-RSP) to the mobile unit, which leads to the activation of the new CID, assuming that the base station accepts the DSA-REQ. The mobile unit will then respond with a dynamic service addition acknowledgement (DSA-ACK).
As noted earlier, the existing PSC with which the mobile is currently associated will not contain the new CID. As such, the mobile unit will transmit a sleep request (SLP-REQ) to the base station, which will cause the base station to deactivate the current PSC and respond with a sleep response (SLP-RSP) to the mobile unit. The mobile unit will then transmit another SLP-REQ to the base station, which will define the parameters for the new PSC to accommodate the new CID. In response, the base station will activate the new PSC, which includes the new CID, and will transmit another SLP-RSP to the mobile unit. This SLP-RSP will also specify the start frame for the next sleeping period (i.e., unavailability window). As can be seen, the time before the mobile unit enters the next unavailability window is relatively lengthy. This additional time, however, is necessary because it allows the base station to re-transmit the SLP-RSP if there is a problem with its initial transmission and it permits the base station to perform synchronization procedures, like synchronizing all or some listening periods for multiple PSCs.
It can be clearly seen that there is a substantial amount of overhead and time involved when a mobile unit wishes to activate a new service flow. Because the current PSC must be deactivated, re-defined and reactivated, the mobile unit may not enter sleep mode during this process. Accordingly, this process negatively affects battery life. Moreover, the abundance of messages being exchanged leads to an inefficient use of network resources.